my fish keep getting ill

Question
we have a large tank with 5 goldfish 2 of them have what looks like a bruise around there mouths they are still feeding fine one seems to be shedding its scales from over the mark an both fish have recently had fin rot. can U tell me what this is? also this morning i found one of the others dead with what looked like a cut on its side it had white flesh pocking through but no blood will this affect the others an do U know what it is? thanks

Answer
Hey Ruth,

your fish have a severe infection. The stress from fin rot left them weak, and developed mouth "fungus" as many call it, but it's really a bacterial infection. Get some tetracycline and treat the tank as soon as you can.

Hope you get to it in time! Good luck.